Voyager 2
obtained the best views of Saturn’s moon Enceladus in August 1981.
The surface of Enceladus contains abundant evidence of a complex and active
history. Portions of the satellite have numerous impact craters, implying
great age, while other areas are almost entirely devoid of craters and
are thus much younger. Several fractures are visible and some fractures
are crosscut and offset by subsequent faults. Enceladus has a very bright
surface, reflecting more than 90% of the incident sunlight, so that very
little dark material (dust or rock) can be incorporated into the surface
ice. All these observation indicate that this small satellite (only 500 kilometers
or 300 miles in diameter) remained very active, while other saturnian
satellites became thoroughly saturated with impact craters. The force
behind this activity may be gravitationally driven tidal
forces much like those responsible for the spectacular volcanos on
Io.